geologic risk for washington state - wa - dnr · nile landslide; $22 million in direct costs 2009...

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www.dnr.wa.gov/geology

GEOLOGIC HAZARDS IN WASHINGTON STATE

Washington geological survey

for Washington StateGeologic Risk

LANDSLIDES, VOLCANOES, EARTHQUAKES, AND TSUNAMIS POSE SERIOUS THREATS TO WASHINGTON’S ECONOMY. WHETHER THEY HAPPEN NEXT YEAR OR IN 50 YEARS, LOSSES ARE LIKELY TO BE DEVASTATING, AND UNDERSTANDING OUR RISKS HELPS INCREASE OUR RESILIENCY

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What is geologic risk?

GEOLOGIC RISK CAN BE DEFINED AS THE COMBINATION OF HAZARD, VALUE, AND VULNERABILITY 1

TSUNAM

I

EARTHQUAKE

LAND

SLIDE VOLCANO

RISK ANALYSIS ANSWERS THREE BASIC QUESTIONS:

1. What geologic hazards exist in the community?

2. What is the likelihood of hazard events occurring?

3. What are the consequences if the hazard event occurs?

value

hazard

vulnerab

ilit

yrisk

TOTAL VALUE OF THE PEOPLE

AN

D PROPERTY IN HAZARD ZONE

VARYING SUSC

EPTI

BILI

TY

TO H

AZARD

S

OF OCCURRENCEIMPACTS AND SOME CHANCEGEOLOGIC EVENT WITH NEGATIVE

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What is geologic risk?

TSUNAM

I

EARTHQUAKE

LAND

SLIDE VOLCANO

size

of c

onse

quen

ces

frequency ofhazard event

infrequent frequentsmall

large

THE CONSEQUENCES OF GEOLOGIC DISASTERS

ARE INVERSELY PROPORTIONAL TO THEIR FREQUENCY

GEOLOGISTS LOOK AT THE GEOLOGIC RECORD TO DETERMINE HOW OFTEN EACH HAZARD IS LIKELY TO OCCUR.

SMALL GEOLOGICEVENTS HAPPEN FREQUENTLY.

HOWEVER, EVERY FEW HUNDRED YEARS, WE CAN EXPECT ONE OR MORE DISASTROUS EVENTS. THESE LARGE EVENTS HAVE LEFT INDELIBLE MARKS ON THE LANDSCAPE AND OUR LIVES.

IN WASHINGTON STATE, THE MOST SIGNIFICANT GEOLOGICAL

HAZARDS ARE EARTHQUAKES, TSUNAMIS, VOLCANIC

ERUPTIONS, AND LANDSLIDES.

OTHER GEOLOGIC HAZARDS INCLUDE SUBSIDENCE ABOVE

IMPROPERLY ABANDONED MINES, RADON, AND OTHER HAZARDOUS

MINERAL EXPOSURE.

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THE ECONOMIC CONSEQUENCES OF A POTENTIAL GEOLOGIC HAZARD ARE DETERMINED BY CALCULATING THE VALUE OF PROPERTY AND INFRASTRUCTURE IN AREAS LIKELY TO BE AFFECTED BY THAT HAZARD

hazard, value, and vulnerability

BENEFIT-COST ANALYSIS

Once the value of loss is known, a benefit-cost analysis may be performed to determine if any mitigation step taken to reduce vulnerability to hazards is an effective use of tax dollars.

HOW IS TOTAL FINANCIAL LOSS CALCULATED?

The total financial worth of a given area is defined as direct loss of people, property, and infrastructure. One could go a step further and add in the monetary value of losses that would occur from disruption of the local or regional economy after a major disaster.FEMA considers a statistical life to be on average worth $6.3 million. This is the amount FEMA uses in benefit-cost analyses.

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annualizing loss

VERTICAL TSUNAMI EVACUATION STRUCTURE

COST = ~$2 million

>1,000LIVES SPARED

GEOLOGIC BENEFIT-COST ANALYSIS IN ACTION: The Ocosta Elementary School Vertical Tsunami Evacuation StructureIn 2012, Grays Harbor county residents voted on a bond measure to add a vertical tsunami evacuation structure—worth ~$2 million—to the Ocosta Elementary school. The 10,000 square foot structure is designed to be a safe refuge for 1,000 coastal evacuees, where much of the land will likely be inundated during a tsunami from which escape on foot is extremely challenging. The benefit-cost analysis for building this structure was simple, as the low cost was easily outweighed by the lives that will be saved by its construction. Additional vertical evacuation structures in coastal communities in Pacific County are now in the the planning stages.

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CA

SC

AD

I A S

UB

DU

CT

I ON

ZO

NE

SEATTLE

TACOMA

YAKIMA

WALLAWALLA

earthquakes

Washington has a high earthquake hazard and has experienced ~15 earthquakes that have caused building damage since 1872. Additionally, geologic evidence demonstrates substantial hazard from faults that have not ruptured since European settlement of the Pacific Northwest. Many of these faults are capable of earthquakes larger than magnitude (M)6.5 at shallow—and therefore highly damaging—depths.

An earthquake scenario for the Seattle Fault shows estimated losses for a M6.7 event would be about $33 billion. 2 Additionally, there is substantial evidence that the Cascadia subduction zone is active and has generated earthquakes greater than M9.0. 3a df adfasdfa dfa df adf f adf fad dfadf dfadfasdf d d ddd dddhdh dh hdh hdhh h dh hhhhh h h hd hhh hhh h

WASHINGTON STATE IS RANKED SECOND IN TERMS OF SEISMIC RISK IN THE NATION

THE 1994 M6.7 NORTHRIDGE, CAEARTHQUAKE KILLED 60 PEOPLE

AND COST UP TO $40 BILLION(IN 1994 DOLLARS)

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CA

SC

AD

I A S

UB

DU

CT

I ON

ZO

NE

SEATTLE

TACOMA

YAKIMA

WALLAWALLA

earthquakes

Faults are breaks in the Earth’s crust that form from tectonic stresses. Rupture occurs

along faults during earthquakes. Most of Washington’s faults have not ruptured since

European settlement of the Pacific Northwest.

damagingearthquakesince 1872

activefault

EARTHQUAKES ON THE CASCADIA SUBDUCTION ZONE RECUR ON AN AVERAGE OF EVERY 500 YEARS OR SO.THE LAST OCCURRED IN AD 1700, BUT MAJOR QUAKES CAN RECUR EVERY 200 TO 1,000 YEARS.

500 YEARS

FOR WASHINGTON STATE, THE IMPACT OF A M9.0 CASCADIA SUBDUCTION ZONE EARTHQUAKE HAS BEEN ESTIMATED AT $49 BILLION 4

61,420 WASHINGTONIANS LIVE IN AREAS HIGHLY VULNERABLE TO LIQUEFACTION DURING AN EARTHQUAKE

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tsunamis

SEATTLE

TACOMA

GRAYSHARBOR

SANJUANISLANDS

BELLINGHAM

STRAIT OF JUAN DE FUCAO

UTE

R C

OA

ST

ON AVERAGE, CASCADIA SUBDUCTION ZONE EARTHQUAKES GENERATE

TSUNAMIS EVERY 500 YEARS

TSUNAMI RISK CHANGES WITH THE SEASONS

as coastal populations increase dramatically

in summer months

Washington has a moderate hazard of distantly generated tsunamis. The tsunami associated with the 1964 M9.2 Alaska earthquake was the largest historic event in Washington. Damage estimates were more than $775,000 to homes and bridges and more than $1.5 million (both in 2016 dollars) to oyster beds in sparsely populated Willapa Bay. Tsunamis generated locally pose a much greater hazard, both because they arrive quickly and because they can be much larger than distantly generated tsunamis—as high as 50 feet in some areas. Geologic evidence demonstrates that a tsunami was generated by an earthquake on the Seattle fault about 1,000 years ago.The largest tsunami in Washington in the last 500 years was generated on the Cascadia subduction zone on January 26, 1700. Sand sheets deposited by it are found from British Columbia to northern California, and it was recorded in both Native American and Japanese records. 3

<50K

>200K

POPU

LATION

RAIN

Y

SEASON

TOURIST SEA

SON

POPULATI

ON

Red areas indicate tsunami inundation modeling coverage to date

2011 TOHOKU TSUNAMI ~$300 billion in total damages15,894 fatalities

47,863 WASHINGTONIANS

LIVE IN THESE HAZARD ZONES

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ON AVERAGE, CASCADIA SUBDUCTION ZONE EARTHQUAKES GENERATE

TSUNAMIS EVERY 500 YEARS

tsunamis

A TSUNAMI IN THE SEATTLE AREA FROM A SEATTLE FAULT EARTHQUAKE HAS A RECURRENCE INTERVAL OF ~2,500 YEARS 2

The assessed value in the tsunami inundation zone along the outer coast and the Strait of Juan de Fuca is ~$4.5 billion, and businesses in the zone generate $4.6 billion in annual sales volume. 11 Fragility curves (the damage vulnerability of buildings for a geologic event) have yet to be developed for tsunamis, but the state of Oregon has adopted 25% of total value for its damage estimates. That would suggest ~$1 billion in property losses and a total loss of business revenue generated there. Total economic losses in Washington would likely exceed $6 billion in the

first year. Loss is compounded when considering that ground subsidence accompanying these events takes several decades to rebound, significantly delaying any rebuilding. Loss of life in a tsunami depends largely upon time of year, time of day, and citizen response. A reasonable estimate for fatalities during a Cascadia subduction zone tsunami is 10,000. FEMA’s benefit-cost model currently assumes the Value of a Statistical Life of $6.3 million, yielding an estimated loss of $63 billion from loss of life alone.

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2014 SR530

Landslide; 43 deaths,

>$80 million in damage

2013 Ledgewood-Bonair

Landslide; 2 homes destroyed

2009 winter storm

>1,500 landslides;$61 million in

FEMA assistance

2009 Nile Landslide; $22 million in

direct costs

2009 Most recent

Lake Roosevelt landslide and

tsunami

2007winter storm

>2,000landslides;$82 million

in FEMA assistance

2006 Rockcrusher Hill

Landlside;>$7 million repair to U.S. Hwy 101

2006 winter storms $7.3 million in

damage to infrastructure

2001Nisqually

Earthquake;>$34.3 million in landslide damage

1999 Carlyon Beach

Landslide;33 homes lost

1998Aldercrest-Banyon



1998Allyn Curves Landslides;

$10–15 million in damage to SR-3

1994Peters Road Landslide;


1992Satus Pass Landslide;

$5 million in damage to U.S. Hwy 97

1990Clallam County

Landslides;$10 million in

damage to SR-112

1987Prosser

Landslides;$10–15 million in damage to Interstate 82

~1500Bonneville Landslide;

blocked Columbia River ~1700

Cascadia subduction zone earthquake

triggered numerous landslides

1872North Cascades

earthquake triggered a landslide that

dammed the Columbia River

1894Puyallup River deltasubmarine landslide

kills 2, destroys railroad track and roadway

1949Puget Sound

earthquake triggers widespread landslides

1965April 29th earthquake

near Tacoma triggered 21 landslides within 60

miles of epicenter

1980Mount St. Helens

eruption unleashed by largest debris avalanche in

recorded history

1996–1997winter storms

damage or destroy nearly 8,000 homes

1990KM Mountain

Landslide;$5 million in

damage

landslides

Landslides are one of the most frequently occurring natural hazards, but they’re notoriously difficult to quantify both in terms of frequency and cost. Inventories of landslides for the state are not comprehensive, and in most cases, landslides are neither noticed nor reported.

Extreme winter precipitation events in western Washington can produce more than 1,500 landslides in a period of a few hours to weeks. And large, slow-moving slides destroy or damage homes and roads several times per month every winter.

Large and damaging events, such as the SR-530 (Oso) landslide or Aldercrest-Banyon in Kelso happen less frequently, but cost millions, and most of this damage is not covered by insurance. FEMA is relied upon in these large events to assist in loss recovery. Federal assistance frequently recovers only about 20 cents on the dollar. If no federal disaster declaration is made, assistance is more often zero.

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2014 SR530

Landslide; 43 deaths,


2013 Ledgewood-Bonair

Landslide; 2 homes destroyed

2009 winter storm

>1,500 landslides;$61 million in

FEMA assistance

2009 Nile Landslide; $22 million in

direct costs

2009 Most recent

Lake Roosevelt landslide and

tsunami

2007winter storm

>2,000landslides;$82 million

in FEMA assistance

2006 Rockcrusher Hill

Landlside;>$7 million repair to U.S. Hwy 101

2006 winter storms $7.3 million in

damage to infrastructure

2001Nisqually

Earthquake;>$34.3 million in landslide damage

1999 Carlyon Beach


1998Aldercrest-Banyon



1998Allyn Curves Landslides;


1994Peters Road Landslide;


1992Satus Pass Landslide;

$5 million in damage to U.S. Hwy 97

1990Clallam County

Landslides;$10 million in

damage to SR-112

1987Prosser

Landslides;$10–15 million in damage to Interstate 82

~1500Bonneville Landslide;

blocked Columbia River ~1700

Cascadia subduction zone earthquake

triggered numerous landslides

1872North Cascades

earthquake triggered a landslide that

dammed the Columbia River

1894Puyallup River deltasubmarine landslide

kills 2, destroys railroad track and roadway

1949Puget Sound

earthquake triggers widespread landslides

1965April 29th earthquake

near Tacoma triggered 21 landslides within 60

miles of epicenter

1980Mount St. Helens

eruption unleashed by largest debris avalanche in

recorded history

1996–1997winter storms

damage or destroy nearly 8,000 homes

1990KM Mountain

Landslide;$5 million in

damage

landslides

THE 2001 NISQUALLY EARTHQUAKE CAUSED

LANDSLIDE DAMAGE OF >$34.3 MILLION 7

(IN 2001 DOLLARS)

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volcanoes

THE PRINCIPAL HAZARDS POSEDBY VOLCANOES ARE ASH FALL AND LAHARS

LAHARS THAT TRAVEL A SIGNIFICANT DISTANCE FROM THE VOLCANO HAVE RECURRENCE INTERVALS ON THE ORDER OF 500 YEARS

Lahars, or volcanic debris flows, can travel far from the volcano and inundate areas with mud tens of feet thick. About 600 years ago, a large lahar buried the present site of the city of Orting 30 feet deep and likely continued to flow down the Puyallup River to Puget Sound. If this were to happen today, damage to structures would total an estimated $13 billion. 8

Mount Rainier, Glacier Peak, and Mount Baker all pose this level of lahar hazard to significant population centers.

Mount St. Helens (at least twelve eruptions in the last 4,000 years) and Glacier Peak (at least six eruptions in the last 4,000 years) are the Washington volcanoes most likely to produce ash. 9 Ash eruptions pose a significant hazard to aircraft, and accumulations of ash can cause severe impact damage, respiratory problems, short-circuiting of electrical equipment, reduced visibility, fouling of machinery, and burial of structures, potentially causing roof collapse. Ash in a lateral blast can have devastating impacts near the volcano.

ASH FALL

LAHARS

500,583WASHINGTONIANS

LIVE IN VOLCANO HAZARD ZONES

AREAS IMPAC TED BY

LARG ELY

D

EPEND UPON THE P R E VA

ILIN

G W

IND

DIR

EC

TIO

N

VOLCAN I C A S H

DURING E RUPTIO NS

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volcanoes

MOUNTBAKER

GLACIERPEAK

MOUNTRAINIER

MOUNTADAMS

MOUNTST. HELENS

500,583WASHINGTONIANS

LIVE IN VOLCANO HAZARD ZONES

THE 1980 ERUPTION OF MOUNT ST. HELENS KILLED 57 PEOPLE AND COST AT LEAST $2.9 BILLION IN 2016 DOLLARS 9

volcano hazard zones, excluding ash fall

At present, only two river valleys near Mount Rainier

have lahar warning systems in place—other valleys have

none

RISK IS INCREASINGBetween 1990 and 2010,

expansion into lahar hazard zones increased by 48,080 residents 10

areas with lahar warning systems in place

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MOUNTBAKER

GLACIERPEAK

MOUNTRAINIER

MOUNTADAMS

MOUNTST. HELENS

SEATTLE

TACOMA

SANJUAN

ISLANDS

BELLINGHAM

STRAIT OF JUAN DE FUCA

OU

TER

CO

AS

T

EVERETT

V E R T I C A LE V A C U A T I O NS T R U C T U R E

L A H A RW A R N I N GS Y S T E M

WAYS TO REDUCE RISK AND LESSEN IMPACTS

● Evaluate geologic hazards at statewide level

● Make schools structurally resilient ● Require utility providers to identify

and mitigate for vulnerabilities in systems before, during, and after an emergency

● Identify and replace aging or vulnerable infrastructure in areas of high seismic hazard

● Build additional vertical tsunami evacuation structures in vulnerable coastal communities to reduce loss of life

● Reinforce or replace unreinforced masonry buildings to better withstand shaking ● Enforce and update building codes ● Encourage and facilitate emergency planning at a community level ● Ensure continuity of health care after emergencies

Tsunami or lahar sirenVertical evacuation structureTsunami inundation modeling coverageVolcanic hazard zoneLahar warning system in place

resiliency

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value

hazard

vulnerab

ilit

yriskvalue

hazard

vulnerab

ilit

y

risk

value

hazard

vuln

erab

ilit

y

RISK CAN BE REDUCED BY: ● mitigate the hazard

through improvement of soil engineering properties

● limiting the value residing in hazard zones with improved hazard mapping, land-use planning, preparedness, and evacuation techniques

● limiting vulnerability to hazards, through improved building codes or relatively inexpensive seismic retrofits

REFERENCES CITED

1. Dibble, R. R.; Nairn, I. A; Neall, V. E., 1985, Volcanic hazards of North Island, New Zealand—Overview: Journal of Geodynamics, v. 3, pp. 369-396.

2. Earthquake Engineering Research Institute and Washington Military Department Emergency Management Division, 2005, Scenario for a Magnitude 6.7 earthquake on the Seattle Fault: Earthquake Engineering Research Institute and Washington Military Department Emergency Management Division, 162 p.

3. Atwater, B. F.; Satoko, M.; Satake, K.; Yoshinobu, T.; Kazue, U.; Yamaguchi, D. K., 2005, The orphan tsunami of 1700—Japanese clues to a parent earthquake in North America: U.S. Geological Survey Professional Paper 1707, 133 p.

4. Washington State Emergency Management Council—Seismic Safety Committee, 2012, Resilient Washington State—A framework for minimizing loss and improving statewide recovery after an earthquake: Washington Division of Geology and Earth Resources Information Circular 114, 33 p.

5. Atwater, B. F.; Moore, Andrew L., 1992, A tsunami about 1000 years ago in Puget Sound, Washington: Science, v. 258, no. 5088, p. 1614-1617.

6. Wood, N.; Soulard, C., 2008, Variations in community exposure and sensitivity to tsunami hazards on the open-ocean and Strait of Juan de Fuca coasts of Washington: U.S. Geological Survey Scientific Investigations Report 2008-5004, 34 p.

7. Highland, L. M., 2003, An account of preliminary landslide damage and losses resulting from the February 28, 2001, Nisqually, Washington, Earthquake: U.S. Geological Survey Open-File Report 03-211.

8. Cakir, Recep; Walsh, T. J., 2012, Loss estimation pilot project for lahar hazards from Mount Rainier, Washington: Washington Division of Geology and Earth Resources Information Circular 113, 17 p.

9. Washington Emergency Management Division, 2008, Washington State enhanced hazard mitigation plan: Washington Military Department.

10. Diefenbach, A. K.; Wood, N. J.; Ewert, J. W., 2015, Variations in community exposure to lahar hazards from multiple volcanoes in Washington State (USA): Journal of Applied Volcanology, v. 4, no. 4, 14 p.

references

16 Washington geological survey

http://www.dnr.wa.gov/geology

WE WORK TO REDUCE RISK AND FUTURE LOSSES FROM GEOLOGIC HAZARDS BY RAISING PUBLIC

AWARENESS AND INFORMING TRAINED EXPERTS.

HAZARDMAPPING

TSUNAMIINUNDATION

MODELING

SCIENCEADVISORS

ACTIVE FAULTSTUDIES

LOCALJURISDICTIONASSISTANCE

EDUCATION ANDOUTREACH

EMERGENCYRESPONSE

SOCIO-ECONOMIC LOSS MODELING

WITHOUT GEOLOGICAL HAZARD ASSESSMENTS, RISKS WOULD BE UNKNOWN, AND BUILDING STANDARDS

WOULD BE BASED ON MERE GUESSWORK.

A RESILIENT SOCIETY PLANS FOR UNSCHEDULED EVENTS.

geologic risk for washington state - wa - dnr · nile landslide; $22 million in direct costs 2009...

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